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Problem Statement: The error saying there are missing engine file(s) appears when trying to run a simulation in Aspen Plus | Solution: This often happens when the user, or when the template file the user used to build the model, contains a reference to a user databank that does not exist.
The remedy is fairly easy:
1. Click on the DATA pull-down menu in Aspen Plus and then click on COMPONENTS
2. Click on the DATABANKS tab at the ... |
Problem Statement: It is possible to specify different properties for the two sides of a HeatX block? | Solution: Indeed, it is possible to specify different property methods for the hot and cold sides of a HeatX block. One case where this is needed is if you want to model water or steam properties accurately using steam tables (STEAM-TA, STEAMNBS, or STMNBS2) and model the process stream using some other property method... |
Problem Statement: What are the flash types available in Aspen Plus CAPE OPEN? | Solution: PVF which requires properties Pressure and PhaseFraction for phase vapor and basis mole to be set in the material object
TVF which requires properties Temperature and PhaseFraction for phase vapor and basis mole
PLF which requires properties Pressure and PhaseFraction for phase liquid and basis mole
TLF which... |
Problem Statement: How is a partial condenser handled in the shortcut distillation block Distl? | Solution: Distl performs shortcut distillation rating calculations using the Edminster approach for a single-feed, two-product distillation column. Distl assumes constant mole overflow and constant relative volatilities. The column can have either a partial or total condenser.
However, as opposed to a RadFrac block, a ... |
Problem Statement: Often times, there is no measurement of a column's product flow rates, or the measurement devices are unreliable/rarely calibrated. If accurate Gas Chromatograph (GC) analysis data is available for each product, can Aspen Plus determine the flow rate of each product? | Solution: Aspen Plus' DATA-Fit feature is capable of regressing the product rates from know compositions. In the attached example the spreadsheet lists the GC composition data, highlighted in Yellow. The GC data is entered on the DATA | Model Analysis Tools | Data Fit | Data Set forms.
The attached Aspen Plus model ass... |
Problem Statement: Is it possible to color the streams in a flowsheet to make it easier to trace streams in a large model? | Solution: Starting in version 12 and later, the material streams have a Color & Style attribute as seen in the screenshot below.
To change a stream color, do the following:
1. Go to the flowsheet view in Aspen Plus
2. Left click on the stream or stream label to highlight the stream
3. Right click on the str... |
Problem Statement: When comparing the liquid enthalpy with the solid enthalpy of a component in some simulations, the enthalpy difference between the phases does not equal the heat of fusion (crystalization). Why would this discrepancy occur? | Solution: There are two ways commonly used in Aspen Plus to calculate the solid component enthalpy: the Barin equations (CPSXPn) and the solid heat capacity method (CPSDIP).
The Barin method uses one set of parameters (the CPxXPn parameters) to calculate all of the thermodynamic properties. There are parameters for eac... |
Problem Statement: The electrolyte template and the electrolyte wizard sets the databank search order as follows:
ASPENPCD
AQUEOUS
SOLIDS
INORGANIC
PURE1x
Is this the way that the search order should be for electrolyte application? | Solution: Yes, this is the order because all of the parameters in our electrolyte databanks were regressed using this order. If there is a problem, the parameter from a more recent version can be entered manually on the forms. Since the other parameters used are regressed with the order mentioned, care should be used.
... |
Problem Statement: If you watch the control panel in an Aspen Plus run that was launched from an Excel spreadsheet using Visual Basic (for applications, VBA), the control panel results are not updated until the simulation engine finishes the run. Why? | Solution: Starting with version 11.1, the control panel updates were shut off until the run completes for automated runs from VBA. This step was taken to speed the execution.
Please try the following items:
Instead of using the run method, try the Run2 method, i.e. go_simulation.engine.run2 instead of go_simulation.eng... |
Problem Statement: Aspen Plus customer gets the following error during System Boot
trctrl.exe encounters problem on boot up | Solution: This is the startup service program to be used with Dais and it is not needed to run Aspen Plus.
Please Note: To disable this service, user needs to have system administrative privileges on that system.
To disable this service do as follows:
Right click mouse on My Computer Icon on your desk top and select Ma... |
Problem Statement: What is the source for the Kij's that are in the binary databanks? | Solution: Kij?s for Peng-Robinson, RKS, Lee-Kesler Plocker came from
Vapor-Liquid Equilibria for Mixtures of Low Boiling Substances, H. Knapp, R. Doring, L. Oellrich, U. Plocker and J. M. Prausnitz, Dechema Chemistry data Series, Vol. VI.
Pure component and Kij?s for BWR-Lee-Starling came from
M.R. Brule, C.T. Lin, L... |
Problem Statement: If I use year as a flow unit, how many days does Aspen Plus consider in a year? | Solution: Aspen Plus will consider a year to have 365.25 days. This takes into account leap year. So if you have a flow of mass/day you would multiply it by 365.25 to get the mass/year.
Keywords: year, day, flow, units
References: None |
Problem Statement: During the calculation of a dynamic pressure relief scenario, Aspen Plus issues the following message:
* WARNING
DISENGAGEMENT CALCULATIONS DID NOT CONVERGE AT 2.828389D+03 SEC
What is the meaning of this message? | Solution: When the user chooses bubbly or churn-turbulent disengagement, there is an iterative
calculation to calculate the vapor fraction leaving the vessel at each time point. The warning
message is saying that this calculation failed to converge. If you make a plot of vent flow vs.
time, you can see it happens right... |
Problem Statement: Why are the Aspen Plus NRTL model equations different than the equations in the original Renon paper (Renon, H. and J.M. Prausitz, Local Compositions in Thermodynamic Excess Functions for Liquid Mixtures, AIChE Journal, 14 (1) 135 (1968) ). | Solution: See page 3-73 of the Physical Properties Methods and Models referece manual for the NRTL equation for activity coefficient. This is an extension of the original model presented in the above paper.
In the Aspen Plus implementation of NRTL:
tau,ij = aij + bij/T + eij lnT + fij/T
Gij = exp(-alpha,ij Sij)
alpha,i... |
Problem Statement: What is the foaming index and what is a reasonable value? | Solution: Foaming or Marangoni index represents the tendency of a liquid mixture to expand due to foaming effects. The values are reported on the RadFrac\Profiles\Hydraulics sheet when the Include Hydraulic Parameters is checked on the RadFrac\Report\Property Options.
The Foaming index is defined as:
Foam-Index = Sigma... |
Problem Statement: What does it mean when variable names are not found and phases are being dropped in EO Reinitialization? How do you suppress these warning messages? | Solution: All warning messages are reported according to the diagnostic level on the Data | Setup | Diagnostics page. It is not recommended to reduce the below the default level as any indications that problems have been encountered may be overlooked causing erroneous results.
When doing an Equation-Oriented (EO) sim... |
Problem Statement: When using the COMPLEX method to converge an optimization problem, what is the definition of STEP-SIZE? How is STEP-SIZE used in generating the initial simplex? | Solution: STEP-SIZE specifies the fraction of the range (for VARY variables) that is used to generate the points in the initial simplex. Note that a different STEP-SIZE can be specified for each VARY variable. New points in the simplex are determined according to the following equation:
S(I) = LB(I) + RANDOM STEP-SIZE(... |
Problem Statement: What is the definition of the flash tolerance? | Solution: The flash calculation in Aspen Plus is a modified inside-out algorithm (by Boston and Britt). The algorithm linearizes the equations and these linear parameters are used in the error check. The parameters replace the primitive variables of temperature, pressure, vapor and liquid compositions, phase ratio, and... |
Problem Statement: What are the units of measurement for GMELCD?
On the input forms, there is a temperature field; so one can switch between C, F, K and R.
However, looking at the databank values, if I switch from C to K, the values stay the same. If I switch from C to F the values will change. Does it make sense to sw... | Solution: When GMELCD is available, absolute temperature units are used (K or R). This is the case whenever we have a term with 1/T or ln(T) -- because units conversion cannot be done if it is C or F. In this case, we have D/T.
Fixed in Version
The 2006 online help for GMELCD, GMELCE, NRTL, and CPDIEC will be updat... |
Problem Statement: Three equations are available for pure component liquid molar volume (VL): the Rackett equation, the DIPPR equation, and the IK-CAPE equation. The DIPPR equation is used if the parameter DNLDIP is available for a given component. The Rackett equation is used if the parameter RKTZRA is available. The ... | Solution: What is called the Rackett model for pure component liquid molar volume (VL=VL01 on the Property Method\Routes sheet or
VL=VL0RKT on the Property Method\Models sheet)
is really the RackettDIPPRIKCape model, but
that name is too long so we shorten it to Rackett.
The default order is as follows if multiple para... |
Problem Statement: What mixing rule is used for molar volume (VL) when components are specified with Tabpoly? | Solution: If Tabpoly is used for VL then the mixing rule for VL (and indirectly density) will be ideal.
The equation is
VL(mixture) = Sum ((VLi) * (xi)
where xi is the molefraction.
This will be used for all components. The built in mixing rules for Rackett will not be used.
For more information about Tabpoly seeSoluti... |
Problem Statement: How do I access stream properties via ActiveX for a simulation with multiple substreams or that have stream classes other than CONVEN? For example how to I get the total density for a stream of class MXCISOLID? | Solution: Using the variable explorer in Aspen Plus the path to density property for a stream named IN-DRIER is
Application.Tree.Data.Streams.IN-DRIER.Output.STRM_UPP.RHOMX.$TOTAL.TOTAL
An example function in VBA that would return a requested stream property might look as follows:
Function CalcProperty (strStreamName,s... |
Problem Statement: How do you report the reaction rates calculated by a user kinetic reaction? | Solution: The existing user variables feature available in RPLUG or RBATCH can be used to print the reaction rates calculated internally by user kinetics subroutines. This feature is used extensively in Polymers Plus to store and report reaction rates and other intermediate calculations (radical concentrations, etc) in... |
Problem Statement: Are the RON and MON stored in the Aspen Plus Pure Component databanks for conventional components? If so, how do I retrieve the information into the Graphical User Interface ? | Solution: For the PURExx Databanks, the Research Octane Number (RON) and Motor Octane Number (MON) are stored in the pure component databanks; however, they are not retrieved automatically when using Tools/Retrieve Parameter Results...
For Release 9.3 and 10, add the parameters by going to Properties/Advanced/User-Para... |
Problem Statement: Where are the input fields for the driving force coefficients A B C D under General reaction LHHW or GLHHW?
With Reactions/LHHW you can enter parameters A, B, C, D (coefficients for driving force constant) for terms 1 and 2 of the driving force expression.
With Reactions/General/LHHW or Reactions... | Solution: LHHW and GLHHW in the GENERAL reaction type is assuming k1 (for forward reaction) is 1 and k2 (for backward reaction) is 0. Therefore, the user does not have to enter the coefficients A, B, C and D for driving force. The link to General LHHW Kinetic Sheet from General Kinetic Sheet is misleading, because the ... |
Problem Statement: Is it possible to handle dilute | Solution: s in the Aspen Plus/FactSage/Chemapp interface?
Solution
Using the diluteSolution capability in FactSage 5.3 with the Aspen Plus/FactSage/Chemapp interface is described below and an example is attached.
Background
FactSage 5.3 has the capability to add components to an existing FactSageSolution. The added co... |
Problem Statement: Service Pack installation disappears after package install is initiated | Solution: Service Pack installation starts by registry cleanup and it takes a long time for this task. The cleanup process goes on in the background and has installation has not been terminated. Customer should leave the installation and come back to it after a while. After Registry cleanup, Service Pack installation w... |
Problem Statement: How does Aspen Plus calculates the THYDRATE and PHYDRATE properties used to predict the temperature and pressure of hydrate formation? | Solution: The ability to predict hydrate formation is vital in the design and operations in gas processing plants. The value is in defining how much inhibitors must be added to avoid hydrate formation of a system of a given composition, temperature and pressure. The goal is to prevent the hydrates from clogging equipme... |
Problem Statement: How is Ergun's equation used in RPlug? More specifically, how does Aspen Plus evaluate the following with respect to Ergun's equation?
1. What are the value of the Ergun A and B parameters used?
2. How is the pressure drop scale factor used?
3. Please explain exactly how particle diameter is used.
... | Solution: Ergun's equation is suitable for computing the pressure drop across packed bed reactors, and as such can be applied within the RPlug unit operation model.
1) The Ergun A and B parameters are the turbulent term and laminar term respectively. In Aspen Plus the turbulent term is set to 150, and the laminar ter... |
Problem Statement: Is there an option to secure property parameters used in a simulation? | Solution: Aspen Plus V7.0 includes a new feature to allow the property parameters (constants such as critical parameters - TC, correlation coefficients such as PLXANT, binary parameters such as NRTL, pair parameters such as GMELCC) used in the simulation to be secured in the following manners through the use of restric... |
Problem Statement: Is it possible to show the Joule Thompson effect in Aspen Plus ? | Solution: The property routines in Aspen Plus automatically take account of the Joule Thompson effect. For example, if you use an equation of state it is reflected in the enthalpy departure term.
The Joule-Thompson (JT) effect is the inversion of the JT coefficent:
(dT/dP) at constant H
For example (Perry 6th edition p... |
Problem Statement: When using ActiveX automation with Aspen Plus, how to activate and de-activate a node (e.g. a design-specifications or a calculator block)? How is it possible to hide and reveal a node? | Solution: To activate a node, use the attribute value HAP_ACTIVATE STATE and set it to HAPP_ENABLE_ACTIVATE. For example, assuming one wants to deactivate calculator block C-1:
mySim.Tree.FindNode(\Data\Flowsheeting Options\Calculator\C-1).AttributeValue(HAP_ACTIVATESTATE) = HAPP_ENABLE_DEACTIVATE
To activate the same ... |
Problem Statement: Is it possible to use pressure relief in Aspen Plus with a stream that includes an assay? | Solution: You cannot specify a stream composition on the Flowsheeting Options | Pres Relief | Setup | Stream tab or the vessel composition on the Setup | Vessel Contents tab. However, you can reference a stream with an assay.
An example file is attached.
Keywords: None
References: None |
Problem Statement: When using the Cyclone model the message LIQUID EXISTS IN MIXED SUBSTREAM appears and the model does not calculate correctly. | Solution: This happens when the the cyclone is fed a liquid fraction in a stream, the Cyclone model needs to only be fed an all vapor stream(vapor fraction =1) in order for the model to function correctly. This error can be remedied by making sure the feed to the cyclone is adjusted to an all vapor stream.
Keywords: Li... |
Problem Statement: Why aren't Fortran variables in Design-Specs updated from one iteration to the next? | Solution: All the DEFINED variables in DESIGN-SPEC are READ-ONLY variables and the values printed in result form are values before executing any Fortran code . They are NOT updated even if it get changed in the Fortran code. In a design-spec convergence loop, the VARY variable is the only variable that is being manipul... |
Problem Statement: There is a security dongle puts a ppmon.dll into the windows\system32 directory. This causes a loading error, because the OS finds the dongles ppmon.dll rather than ours. The error is Unable to load simulation engine. Probable cause: Insufficient disk space or memory message.
Information about the do... | Solution: Aspen Properties Plus uses a dll called PPMON.DLL which is located in the properties plus folder. In this dll, PP stands for Properties Plus SLEEK Dongle also uses a dll called PPMON.DLL which is located in the System32 folder. In this dll, PP stands for Parallel Port.
This program provides a security-related... |
Problem Statement: What units of measure should be used for parameters in DFMS files used to create a user or inhouse databank? | Solution: The parameters should have SI units. You must enter all data in SI units, because DFMS does not perform units conversion.
Parameter Name
Description
Units
AIT
Auto ignition temperature
K
ANILPT
Aniline point
K
API
Standard API gravity at 60?F
Dimensionless
AROMATIC
Aromatic content (1=aromatic, 0=no... |
Problem Statement: UOSSTAT2 is available in the xml file. What values can UOSSTAT2 have? | Solution: UOSSTAT2 has the following definitions:
UOSSTAT2
Definition
2
Simulation was completed normally
3
Simulation was not completed normally
4
Data regression was completed normally
5
Data regression was completed with errors
6
Assay data analysis was completed normally
7
Assay data analysis was completed ... |
Problem Statement: Can additional properties be printed in the stream summary or report? | Solution: Yes, additional properties can be printed in the stream summary or report file.
In Aspen Plus 10 and higher,
1. From the Data Browser, go to Setup / Report Options / Streams and click on the Property Sets button.
2. Use the arrows to select any number of Property Sets from those in the Available l... |
Problem Statement: What are some typical U values for various types of heat exchanger services? | Solution: For most cases, the default value used in the HeatX block (150 Btu/(F-ft2 - hr)) is far too high. It is best to rate the heat exchanger after specifying it's bundle/shell geometry in the HeatX block's input forms. If you need to make a short-cut approximation, here are some general rules:
Sensible heating/c... |
Problem Statement: What is the PC-SAFT EOS model and its applicability? | Solution: The SAFT (Statistical Associating Fluid Theory) EOS is a rigorous thermodynamic model based on perturbation theory. It evaluates the properties of fluids based on interactions at the molecular level. It is able to separate and quantify the effects of molecular structure and interactions on bulk properties and... |
Problem Statement: Is there an easy way to load Pro/II models into Aspen Plus? | Solution: To convert a Pro/II input keyword file for use with Aspen Plus, there are two primary steps:
1) Open a blank simulation in Aspen Plus and click on TOOLS | OPTIONS and then select the GENERAL tab. Check the box at very bottom of the form to retain the Pro/II block information as in Figure 1, below:
Fig... |
Problem Statement: Why Equation-Oriented (EO) script statements in Global and Local Scripts forms in Aspen plus GUI are not run by Aspen Plus? | Solution: In Aspen plus GUI's Global and Local Scripts forms, scripts statements will not run if they are not formatted properly. When you write EO scripts in these 2 places, do not indent lines by more than 3 initial spaces or else they will be ignored. Also, do not write more than 64 characters per line.
Note that ... |
Problem Statement: What is the syntax for a legacy DFMS input file for binary parameters for an Equation of State model to be used in the customization of the Aspen Properties Enterprise Database (APED)? | Solution: There are two types of parameters, symmetric and unsymmetric ones.
1. Symmetric Parameters kij = kji
Examples of symmetric parameters include SR-POLAR parameters RKUKA0, RKUKA1, and RKUKA2. Symmetric parameter value should appear twice. For example:
PROP-DATA
PROP-LIST RKUKA0 1
BPVAL C2H6O-2 CO2 0.3 0.3
2... |
Problem Statement: Cannot run flowsheet because an outlet or intermediate stream is incomplete. Shouldn't the file be able to run and determine the outlet conditions?
Cause
If any piece of input is entered on the Stream form, the form needs to be completed. This is part of the completeness and consistency checking th... | Solution: Data for intermediate streams is used as an initial guess only if the stream is a tear stream.
If the data is not needed, go to the stream name in the Stream folder of the left hand pane of the Data Browser, right mouse click, and select Clear to remove all data. If the data is needed, complete the form. Use ... |
Problem Statement: Is it possible to change the vapor phase equation of state model when using electrolyte models? For example, how do I model a system with electrolytes and organic acids such as acetic acid? Is there a way to use electrolytes with Hayden O'Connell (HOC)? | Solution: It is possible to change the vapor phase equation of state model for phase equilibria and enthalpy calculations. Before 12.1, it was possible to change the vapor phase equation for phase equilibria calculations, but the enthalpy model did not consistently calculate the correct vapor-phase departure.
The vapor... |
Problem Statement: I've always assumed that when a binary parameter is missing for NRTL, the mixture would behave as ideal. However, in this ternary mixture A, B, C where binary parameters have been specified only for A with B, the activity coefficient for C is not one. Why not?
See the attached file nrtl.bkp. | Solution: In the file nrtl.bkp, set the mole flow of A to zero in the property analysis. You will see that the activity coefficient for B and C are 1, indicating that that the binary mixture behaves as an ideal mixture.
The assumption that when binary parameters are missing (or set to 0), the mixture behaves as ideal i... |
Problem Statement: How to correct error 'Failed to create and load form control: MMComp_Spec.MMComp_Spec_Input'. | Solution: Go to Command prompt and type:
regsvr32 c:\windows\system32\msvbvm60.dll
then all of the form control errors should be solved.
Keywords: Properties
Forms
References: None |
Problem Statement: What is best value of System foaming factor? | Solution: The clear liquid height is the height to which the aerated mass would
collapse in the absence of vapor flow. The clear liquid height gives a measure of the liquid level on the tray and is used in efficiency, flooding, pressure drop calculations. The froth (foam) factor is related to the froth height and the c... |
Problem Statement: What convergence algorithm should be used in RadFrac? | Solution: No single algorithm works all the distillation problems. Aspen Plus offers a group of algorithms and initializaion methods. We recommend the use of the Standard convergence method first for most two- and three-phase columns. It can be used to perform free-water calculations in the condenser or the entire colu... |
Problem Statement: How is it possible to get a better fit of CO2 partial pressure? How does Aspen Calculate new Total Pressure of CO2 since we specify partial press equal to Total Pressure? | Solution: It is better to just fit the CO2 partial pressure since the water partial pressure typically works reasonably well without fitting and inclusion of it in the fit seems to cause DRS convergence difficulties.
The way to accomplish fitting just the CO2 partial pressure is to:
Provide the liquid-phase compositio... |
Problem Statement: What is the Vredeveld power law mixing rules for liquid thermal conductivity? | Solution: The Vredeveld power law mixing rule for liquid thermal conductivity (KLMX) is as follows:
KLMX**expt = SUM [ wi * KLi**expt ]
where wi is weight fraction of component i
and KLi is the pure component thermal conductivity of i
The exponent (expt) can be set using the model option code. The most appropriate valu... |
Problem Statement: Is it possible to view a subset of streams in a specified order on the ResultsSummary\Streams form? | Solution: A customized stream summary file (.TFF) can be created.
Files with the TFF extension (filename.tff) are used by Aspen Plus to format the Stream Summary result form. For more information on TFF files refer to the Aspen Plus User Guide.
The steps are as follows:
Copy one of the existing .TFF files in the Aspen ... |
Problem Statement: How are the values calculated in the Regression / Input / Parameters input form for initial value and upper and lower bound after I run a regression case? Can I turn off the automatic filling in of these values? | Solution: The values of the initial value and upper and lower bounds are filled in depending on the option specified in Run / Settings / Options tab Copy Regression and Estimation results onto Parameters form. We recommend turning this option off initially.
The initial value is the regressed value of the parameter and ... |
Problem Statement: Is it possible to specify the number of exchangers in series and parellel in a HEATX block? | Solution: In 11.1, it is possible to specify the number of exchangers in series using the Shortcut method only. To model exchangers in parallel, a MULT block should be put before and after the HEATX block.
In 12.1, it is possible to specify heat exchangers in series and parallel also for the rigorous method.
The HEATX ... |
Problem Statement: Is it possible to have a reactive distillation and have the product show up in a solid stream? The React-dist does not allow a reaction product in a solid substream. Is there any other way? | Solution: CISOLIDS and NCSOLIDS do not participate in reactions in RadFrac. The reaction needs to be completed using a reactor before or after the RadFrac column.
Keywords: cisolid
ncsolid
References: None |
Problem Statement: Analyzer EO Variables | Solution: Analyzer EO Variables
A change introduced in V7.0 had compatibility effects not reported until now. Adding support for solids to the EO formulation of Analyzer required reformulating the model slightly to make it more like other models. Specifically, the DELTA_ENTH variable was removed, and a new DUTY varia... |
Problem Statement: How does the RStoic conversion specification treat electrolytes? | Solution: When using the True species approach, the conversion will only apply to the true species concentration. For example if you have HCL and H2O completely dissociating into H3O+ and CL-, then a reaction in RStoic using key component HCL will not occur.
When using the Apparent composition approach, the conversion ... |
Problem Statement: After entering Txy data and regressing the NRTL 2 (Bij and Bji) parameters, the sum of square error is very high (over 1 million), and when reviewing the Regression profile results, the estimated temperature in the first row is much higher than the experimental temperature. | Solution: Normally, the temperature data should have good agreement between the experimental and estimated columnar data. However, a common user error, reversing the composition data (entering component A's composition in the component B column) will cause a temperature error, especially if there is a large difference ... |
Problem Statement: Why do my design-specs, and sensitivity analyses require a Fortran compiler when they do not have any Fortran or arithmetic expressions? Also, I have reviewed | Solution: document 104149, and my Calculator block does not contain any arithmetic expressions that require a compiler, yet Aspen Plus produces errors about the missing Fortran compiler?
Solution
When Aspen Plus keeps searching for a Fortran compiler, even though one is not needed, it is because there is a setting that... |
Problem Statement: The unit of measure for HENRY's component data input into Aspen Plus is pressure. However, typically HENRY's component data found in literature are expressed in pressure/concentration such as Atm/(mol/liter). How do you get HENRY's component data calculated in Aspen Plus in the pressure/concentration... | Solution: Ideally, HENRY constants could be calculated with a PROP-SET.
In 2006.5, two new Property Sets were added:
1. GAMUSAQ: Unsymmetic activity coefficient based on the aqueous reference state
This property is calculated from gamma(i in the mixture)/gamma infinity of i in water. GAMUSAQ is different from G... |
Problem Statement: Which property method is best for steam and water properties for pure water streams or for free-water calculations? | Solution: Three methods are available in Aspen Plus:
STEAM-TA (ASME 1967 steam table correlations)
STEAMNBS (NBS/NCR steam tables)
STMNBS2 (NBS/NCR steam tables with a different root search method)
For process calculation purposes, the accuracy of all three methods is adequate.
STEAM-TA method is made up of different c... |
Problem Statement: Is the percent distilled under Stream Analysis | Dist-Curve in mass or volume percentage? | Solution: The percent distilled is on a liquid volume basis.
Keywords: Stream Analysis, Dist-Curve, %DIST, CQ00570745
References: None |
Problem Statement: What does the SOLID component type do? | Solution: If a component is specified as component type SOLID on the Components | Specifications | Selection sheet
It can be defined as a SALT on the CHEMISTRY block.
The Electrolyte Wizard will create components with the SOLID component type for salts.
A component with the SOLID component type can be entered in the CI... |
Problem Statement: I want to refine my ELECNRTL model by including some heat of mixing (HLXS) data in my regressions. The trouble is, ELECNRTL consistently calculates HLXS to be zero. Is this the right way to set up the problem? Should I be using HLXS? Should I be using some other formulation for the excess enthalpy da... | Solution: The ELECNRTL property method is somewhat different from other activity coefficient methods in the sense that heat of mixing (HLXS) is included in liquid mixture enthalpy calculations. For this reason, ELECNRTL is unable to predict the property HLXS. For the same reason, a regression case which uses ELECNRTL i... |
Problem Statement: When using the ENTRL-RK databank for binary components, there is a binary parameter pair for CO2-H20. Where does this parameters come from since CO2 would usually be modeled as a Henry's component? | Solution: Although CO2 is usually supercritical and modeled as a Henry's component when using activity based property methods, there are times when the concentration of CO2 in the liquid phase is too large for only the Henry's method to be applicable.
When a component is declared as a Henry component, the concentration... |
Problem Statement: Why are the valve tray types not updated with more recent designs? | Solution: The design procedures for specific vendor tray types have not been updated for some time. This is primarily due to the fact that it is extremely difficult to get competing vendors to share their tray design procedures with a third party who will have access to not only their design procedure but the procedure... |
Problem Statement: The TEMA sheet gives the weight of shell, weight filled with water and bundle weight. What is the total weight of the shell channel plus the bundle? | Solution: Here are how the three weight results are calculated at the bottom of the TEMA sheet:
Weight per shell:
The weight of the entire heat exchanger. This includes all of the heat exchanger components attached to the shell channel plus the weight of the bundle.
Weight of the bundle:
This is a sub-set of the weight... |
Problem Statement: Is there an alkylation example for Aspen Plus? | Solution: Chapter 15 of Gerald Kaes' Refinery Process Modeling - A Practical Guide to Steady State Modeling of Petroleum Processes, reference deals with process simulation of alkylation production units.
Mr. Kaes has authorized Aspen Tech to publish, on our support website, the companion workshops for his reference in ... |
Problem Statement: With Aspen Plus version 12.1 and higher, the import (read-vars) and export (write-vars) are interpreted more strictly. If import (read-vars) are entered, all other accessed variables are assumed to be export (write-vars), and vice versa. This strictness will uncover inconsistencies in existing Calcul... | Solution: Review calculator blocks to ensure they are correctly specified.
Keywords: calculator
fortran block
References: None |
Problem Statement: I am getting FORTRAN errors in my equation-oriented run and I have user code. It is possible that these errors ome either from my own code or from a defect in Aspen Plus. How do I go about debugging my own code to make sure it is in order? | Solution: Please follow attached Word document.
Keywords: EO
References: None |
Problem Statement: How do you recommend modeling multiple interlinked columns? | Solution: We recommend using RadFrac with the Equation-Oriented (EO) paradigm to model such problems. We think that this approach is more flexible and robust than using MultiFrac. In addition, we are focusing more development resources on RadFrac's algorithms than any other column.
Keywords: column, tower
References: N... |
Problem Statement: What is the recommended upper temperature range of the various pseudocomponent property methods built into Aspen Plus (e.g. API-METH, API, COAL-LIQ, ASPEN) for heavy petroleum applications in terms of the atmospheric equivalent boiling point of the pseudocomponents? | Solution: There are no documented upper limits for these methods from the authors. Our studies showed that the limits vary depend on the property [molecular weight (MW), boiling point (Tb), critical temperatue (Tc), critical pressure (Pc), etc], but most of them would behave properly up to a normal boiling point of abo... |
Problem Statement: Is there a way to tabulate internal energy (U) on the stream summary? | Solution: In 2004.1 and higher, there are new Prop-Set properties U (for a pure component) and UMX (for a mixture) that can be used to report the internal energy.
Keywords: U
References: None |
Problem Statement: How to retrieve pure component parameters such as molecular weight, Tc, etc in Aspen Plus? | Solution: The parameters are stored in databanks specified in the Components Specifications Databanks sheet. By default, Aspen Plus do not display all the pure component parameters on the parameter input forms. The data will be retrieved automatically from the databanks during simulation.
To view the parameters for the... |
Problem Statement: How are prompts added for a user databank? | Solution: To add a two-line prompt for a databank, modify the tbmsg.txt file by adding a
section in the following format at the end of all similar sections in the file:
DBANK HELP mmdbname
one or two line prompt.
>
>
$
$
To create databank hypertext Help:
1. Open the file userdata.rtf using Microsoft Word.
2.... |
Problem Statement: When using the NRTL activity coefficient model, I checked the box on the Properties | Binary interaction | NRTL form to use UNIFAC to estimate all missing parameters. After running the model, I decided to uncheck the box for using UNIFAC to estimate the missing parameters and deleted all of the inter... | Solution: When the Estimate all missing parameters by UNIFAC button is checked, Estimate all missing parameters is selected on the Properties | Estimation | Setup sheet and all binary parameters are selected on the Binary sheet. When the box is unchecked, the binary parameter estimation information is deleted, but the ... |
Problem Statement: What are the governing equations for the NRTL-SAC model used in Aspen Plus? | Solution: NRTL-SAC is a segment contribution activity coefficient model, derived from Polymer NRTL model. NRTL-SAC can be used for fast, qualitative estimation of the solubility of complex organic compounds in common solvents. Conceptually, the model treats the liquid non-ideality of mixtures containing complex organic... |
Problem Statement: What is the difference between DSTWU, Distl and RadFrac column capabilities? | Solution: DSTWU is used for shortcut distillation design
Distl is used for shortcut distillation rating
RadFrac is used for Rigorous rating and design for single columns
Brief description with different capabilities are explained below for your reference
The DSTWU unit operation is designed for single feed, two produ... |
Problem Statement: How is it possible to implement a kinetic model that is based on activities rather than on concentrations? How is the Activity sheet on the Reaction form used? | Solution: The Activity on the Activity sheet of a Reaction form is used to to define reaction activity classes and associate them with reactions. Reaction activity classes are scalar multipliers to the reaction rate. The net reaction rate for a reaction is calculated as the product of the reaction's intrinsic rate and ... |
Problem Statement: Aspen Properties Enterprise Database on V7.0, V7.1 failed to load on HYSYS or Aspen Plus. | Solution: To install SQL Management tool from the link below:
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=c243a5ae-4bd1-4e3d-94b8-5a0f62bf7796
Download the documentation to troubleshoot random APED issues. (See attached)
Manually re-register APED databases from Aspen Properties Database Ma... |
Problem Statement: Is there any documentation concerning how the steam table methods are extrapolated in Aspen Plus? Are there different extrapolation methods for the different methods? | Solution: The extrapolation methods are different for the three different steam table methods in Aspen Plus: STEAM-TA, STEAMNBS, and STMNBS2.
STEAM-TA
The STEAM-TA method is based on the ASME 1967 steam correlation, which is a piece-wise correlation. In this method, different functions are used to represent different r... |
Problem Statement: Why does the pump issue an error saying the feed has more than 0.01% vapor?
FEED HAS MORE THAN 0.01 % VAPOR. OUTLET CONDITIONS | Solution: The pump unit operation in Aspen Plus was designed to handle liquid phases. Those liquid phases can be a single, homogeneous liquid phase, or a two-phase liquid such as water - hydrocarbon(s). In actual plant operations, pumps with unwanted vapor in their feed will experience cavitation and possible mechanica... |
Problem Statement: From when are most recent UNIFAC-DMD parameters? Do they date from end of 1990s or are they more recent (via UNIFAC consortium)?
In the 2004.1 help I find the following:
J. Gmehling, J. Li, and M. Schiller, Ind. Eng. Chem. Res. 32, (1993), pp. 178-193.
Are these the ones used in 2004 and 2004.1? ... | Solution: There were some changes to UNIF-DMD made for 12.1. I have pasted the information from the What's New in Aspen Engineering Suite (AES) 12.1. We included all the published parameters at that time (until 2002). We have not updated it since; therefore, 2006 will not have any updates.
A UNIFAC consortium member is... |
Problem Statement: When modeling electrolytes with ELECNRTL, pure component heat capacity (Cp) for some ions is negative. Why should it be negative? Does it mean anything? Does it make any sense to report Cp for an ion? When dealing with electrolytes and true component, shouldn't we just focus on mixture heat capacity ... | Solution: Ions always exist inSolution together with their counterions to achieve electroneutrality. Consequently, the physically meaningful Cp's are the Cp's for the ion pairs. Cp's for ion pairs should be positive. (Note that we are dealing with Cp's at infinite dilution.)
In order to compute Cp's for ion pairs, th... |
Problem Statement: For a conventional inert solid in a liquid stream, what is the definition of MASSCONC? | Solution: The MASSCONC for a conventional inert solid in a liquid stream is calculated based on the total volume of the liquid and the solid components:
Solid concentration = [mass of solid / volume of (solid + liquid)].
This can be verified by the following steps in the attached example:
1. Define a prop... |
Problem Statement: Service Pack installation disappears after package install is initiated | Solution: Service Pack installation starts by registry cleanup and it takes a long time for this task. The cleanup process goes on in the background and has installation has not been terminated. Customer should leave the installation and come back to it after a while. After Registry cleanup, Service Pack installation w... |
Problem Statement: How does Aspen Plus calculates the THYDRATE and PHYDRATE properties used to predict the temperature and pressure of hydrate formation? | Solution: The ability to predict hydrate formation is vital in the design and operations in gas processing plants. The value is in defining how much inhibitors must be added to avoid hydrate formation of a system of a given composition, temperature and pressure. The goal is to prevent the hydrates from clogging equipme... |
Problem Statement: How is Ergun's equation used in RPlug? More specifically, how does Aspen Plus evaluate the following with respect to Ergun's equation?
1. What are the value of the Ergun A and B parameters used?
2. How is the pressure drop scale factor used?
3. Please explain exactly how particle diameter is used.
... | Solution: Ergun's equation is suitable for computing the pressure drop across packed bed reactors, and as such can be applied within the RPlug unit operation model.
1) The Ergun A and B parameters are the turbulent term and laminar term respectively. In Aspen Plus the turbulent term is set to 150, and the laminar ter... |
Problem Statement: Is there an option to secure property parameters used in a simulation? | Solution: Aspen Plus V7.0 includes a new feature to allow the property parameters (constants such as critical parameters - TC, correlation coefficients such as PLXANT, binary parameters such as NRTL, pair parameters such as GMELCC) used in the simulation to be secured in the following manners through the use of restric... |
Problem Statement: How can I stop my simulation at specific blocks or upon error/warning messages? | Solution: In sequential modular mode, stop points can be used for an interactive simulation. They can be set up through Stop Points from the Run menu or by right clicking on the blocks in the left hand pane of the Control Panel. Users can choose to temporarily halt the simulation either before or after a step, which ca... |
Problem Statement: Does the Aspen Plus input file (*.inp) contain any of the dynamic keywords used to create Aspen Dynamic models? | Solution: The only link between Aspen Plus and Aspen Dynamics is via the Aspen Plus Graphical User Interface. Since the Aspen Plus Simulation Engine has no links to Aspen Dynamics, none of the dynamic input entered in the Aspen Plus Graphical User Interface is written to the Aspen Plus Input file.
Keywords: Aspen Dynam... |
Problem Statement: Why is the vapor from my flash that has a nonvolatile salt in it not at the dew point? | Solution: The vapor in the flash is in equilibrium with the liquid and salt. However, the vapor, taken aside, is superheated. This is a consequence of the presence of the salt causing a boiling point elevation of the whole mixture. If you boil water and salt, there is a boiling point elevation so it will boil at a temp... |
Problem Statement: Is there a way to get a HeatX block running in shortcut mode to calculate the required area? | Solution: Yes, it is possible for HeatX to calculate the required area in the shortcut mode.
Set the HeatX block to have a Calculation type of Rating. Then, enter a guess for the area (see Figure 1) and an outlet process condition as a specification (in this case, the hot outlet stream temperature was set to 140 F). Cl... |
Problem Statement: Why do mixed mode runs, where part of the flowsheet is solved with Equation Oriented (EO) and part is solved with Sequential Modular (SM), take as long as SM-only runs? | Solution: The problem is that EO needs to have good estimates for every stream and unit operation in the flowsheet. The attached .bkp file is a mixed mode flowsheet. The entire simulation runs in SM except for the one Hierarchy block that runs in EO. The hierarchy block needs to be solved via SM first, and then it can ... |
Problem Statement: The physical properties models and methods reference guide says Aspen Plus has a polynomial activity coefficient model used for metallurgical applications. How do I use it? | Solution: This model is very infrequently used, so it does not come in a pre-packaged standard property method. The purpose of this note is to clarify some items explained in the documentation, which you should read first.
To use this model:
1. On the Properties | Specifications sheet, specify an activity coeffic... |
Problem Statement: How can I generate the list of units available in Aspen Plus, for example to verify units introduced in a new version? | Solution: You can use the SDFRPT utility program (System Definition File Report).
Steps:
1. Open a command window using the Aspen Plus Simulation Engine option
2. At the command prompt, type SDFRPT, then press the enter key
3. At the prompt, type UNIT, then press the enter key
4. At the prompt, ... |
Problem Statement: My Radfrac electrolyte simulation converges quickly and without problem when using the apparent component approach. If the true component option is enabled the simulation fails. | Solution: When one switches to the true approach, Aspen Plus has to account for the starting concentrations of the ionic and salt species listed in the component list for all the trays . Since these components did not previously exist while running the apparent mode, it is tries to estimate these concentrations. This w... |
Problem Statement: How do you access a stream property within a Sensitivity, Design Spec, or Calculator block? | Solution: To use a stream property in a Sensitivity, Design Spec or Calculator block, you will need to first define a property set within the Prop-Sets folder and then reference it in desired Object manager. The procedure is outlined below:
1. Navigate to the Properties Prop-Sets folder within the Data browser. C... |
Problem Statement: When using the Cyclone model the message LIQUID EXISTS IN MIXED SUBSTREAM appears and the model does not calculate correctly. | Solution: This happens when the the cyclone is fed a liquid fraction in a stream, the Cyclone model needs to only be fed an all vapor stream(vapor fraction =1) in order for the model to function correctly. This error can be remedied by making sure the feed to the cyclone is adjusted to an all vapor stream.
Keywords: Li... |
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